Superconducting device

A superconducting device comprising a pair of superconducting electrodes, having a thickness, so formed as to have a projection of semiconductor material, formed on a semiconductor substrate, interposed therebetween, the projection having lateral surfaces extending from the semiconductor substrate, and a height in a direction of the thickness of the superconducting electrodes, and a control electrode means for controlling current flowing between the superconducting electrodes, which control electrode means is formed so as to cover at least a part of an upper surface of said projection of semiconductor material, and is separated from said projection by an electric insulator film said control electrode means serving to control a superconducting weak coupling state between said superconducting electrodes, and wherein the lateral surfaces have lateral surface regions extending from the lateral surfaces into the projection, the lateral surface regions having an impurity concentration higher than that of the substrate, the lateral surface regions, having the relatively high impurity concentration, extending the height of the projection from the substrate to a top of the projection, wherein said lateral surface regions having a relatively high impurity concentration region include a first high impurity concentration sub-region, the first high impurity concentration sub-region contacting one of the pair of superconducting electrodes, and the second high impurity concentration sub-region contacting the other of the pair of superconducting electrodes.